1. Technical Field
The present invention relates to a navigation device for reading map data from a recording medium, searching a route to a destination based on the map data, and providing guiding along the route.
2. Background Art
The navigation device reads data on a road map from a predetermined recording medium, and data of accompanying road information, detects the current position by using a global positioning system (GPS), searching a route to a destination set by a user by a predetermined method such as Dijkstra method or the like, and then providing image or voice guiding along the searched route.
For example, a conventional navigation device disclosed in Japanese Patent Application Laid-open No. 9-96532 comprises: an external storage driving means for reproducing and storing a plurality of recording media including a map recording medium for recording map data, a music recording medium for recording music data, a video recording medium for recording video data, and so on; and a temporary storing means for temporarily storing data read by the external storage driving means. In this case, present processing is continued based on the data stored in the temporary storing means. If another function is requested, while the current processing is being executed, based on the read data, a recording medium is switched to another one, and the data recorded in the thus switched recording medium is read out by the external storage driving means, and a requested processing is executed based on the read data. Accordingly, the present processing and the requested processing can be executed simultaneously.
The foregoing configuration of the conventional navigation device enables processing such as route searching or the like, and pre-reading of map data necessary for route guiding, to be executed simultaneously. However, problems including the user""s finding difficulty in knowing a progress in the pre-reading operation of map data and so on, have been inherent. Thus, for example, the pre-reading of map data up to a point, for which the user required route guiding, enabled a map recording medium to be switched to another recording medium. However, it was difficult for the user to determine whether or not the pre-reading to that point was finished.
The present invention was made to solve the foregoing problems, and it is an object of the invention to provide a navigation device for enabling the user to know a progress in the pre-reading operation of map data by notifying the quantity or ratio of the pre-read map data.
In accordance with the present invention, a navigation device is provided, comprising: a route search processing unit for searching a route to a destination based on map data; a pre-reading processing unit for pre-reading the map data necessary for route guiding from a recording medium; a route guiding processing unit for providing a guiding of the route to the destination based on the map data; a calculation unit for calculating a quantity or ratio of the map data pre-read by the pre-reading processing unit; and a notification unit for notifying the quantity or ratio of the map data pre-read by said pre-reading processing unit. This arrangement enables a user to know a progress in the pre-reading operation of the map data, and to instruct an interruption or a termination of the pre-reading when necessary. Thus, it is possible to enhance convenience.
According to the navigation device of the invention, as the map data necessary for route guiding, the pre-reading unit pre-reads map data on an area en route to the destination and a surrounding area thereof. Thus, even when a vehicle moves away from the searched route and enters a surrounding area, it is possible to continue the route guiding only based on the pre-read map data without needing any map recording media.
According to the navigation device of the invention, the calculation unit calculates a distance of a route to a pre-read area as a quantity of the pre-read map data. This arrangement enables the user to know how far the route guiding can be performed without any map recording media.
According to the navigation device of the invention, the calculation unit calculates a sum of distances between joints on the route as a distance on the route.
According to the navigation device of the invention, the calculation unit calculates a ratio of a distance of a route up to the pre-read area and a distance of a total route as a rate of the pre-read map data. This arrangement enables the user to know how far the route guiding can be performed without any map recording media.
According to the navigation device of the invention, the pre-reading processing unit pre-reads the map data necessary for route guiding during the period of non-reading of map data necessary at present. Thus, it is possible to execute pre-reading processing without interrupting the reading of map data necessary for currently executed processing.
According to the navigation device of the invention, the calculation unit calculates a quantity or ratio of map data from a starting point of the route to a pre-read point.
According to the navigation device of the invention, the calculation unit calculates a quantity or ratio of map data from a present position to a pre-read point.
According to the navigation device of the invention, the notification unit displays the quantity or ratio of the pre-read map data by numerical values. This arrangement enables the user to intuitively know how far the route guiding can be performed without any map recording media.
According to the navigation device of the invention, the notification unit displays the quantity or ratio of the pre-read map data by meters. This arrangement enables the user to intuitively know how far the route guiding can be performed without any map recording media.
According to the navigation device of the invention, the notification unit displays the quantity or ratio of the pre-read map data along the displayed route. This arrangement enables the user to intuitively know how far the route guiding can be performed without any map recording media.
According to the navigation device of the invention, the notification unit notifies the quantity or ratio of the pre-read map data by displaying map images different in color between a non pre-read area and a pre-read area. This arrangement enables the user to intuitively know how far the route guiding can be performed without any map recording media.
According to the navigation device of the invention, the notification unit uses an area of displaying the quantity or ratio of the pre-read map data for displaying other data during route searching by the route search processing unit. Thus, it is possible to effectively use the display screen of the display.